A neodymium magnet is a permanent magnet mainly containing a neodymium-iron-boron (Nd—Fe—B)-based intermetallic compound (Nd2Fe14B). The neodymium (Nd) magnet has some advantages of excellent magnetic property, high strength and not expensive manufacturing cost and thus applied for various industrial products so that the amount of production of the neodymium magnet is remarkably increased. As the main use of the neodymium magnet can be exemplified a voice coil motor for a hard disk, a compressor motor of an air conditioner and a motor for a hybrid car. Since the compressor of the air conditioner or the motor of the hybrid car requires high coercive force at high temperature, a neodymium magnet containing dysprosium (Dy) added thereto would be used so as to increase the coercive force. In the future, the consumption of the neodymium magnet containing Dy is much remarkably increased with the increase of the hybrid car, so that it is expected that a large amount of magnet scraps are generated.
A good ore deposit relating to a rare earth element such as Nd and Dy which are raw materials for the Nd magnet is localized in a specific country so that the cost of the rare earth element is likely to be fluctuated due to the export restriction of the specific country. In this point of view, the anxiety for the stable supply of the rare earth is growing. Moreover, since an ore containing the rare earth element also contains a radioactive element such as uranium (U) and/or thorium (Th), the mining of the ore may cause serious problems such as an environmental destruction and a concentrated radioactive substance treatment. As for Dy, there is an ion adsorptive ore deposit almost free from such a radioactive element, but this type of deposit is geologically rare, and in addition may destroy the environment in the vicinity of the ore deposit because an acid is injected into the soil of the ore deposit in the mining of the ore and the extraction of rare earth elements from the ore. Since Nd is relatively rich as a resource, there is not almost anxiety for the exhaust of Nd. However, when Nd is obtained from the corresponding ore, the problem of treating the radioactive elements contained therein cannot be avoided. In view of the environmental destruction relating to the mining and refining of the ore and the increase in demand of Nd in the future, the recovery of Nd from the product scraps is important subject. At present, however, the recycle of the rare earth element from products is not almost conducted except the recycle of the rare earth element from large sized products such as magnets for MRI.
By the way, as the recycle method of the Nd magnet, the recovering method where an iron chloride is contacted with the scraps of rare earth magnets or the magnet sludges thereof (the sludge of the rare earth magnets) so that the intended rare earth elements are recovered as the corresponding chlorides is proposed (refer to Reference 1). In the invention, the mixture of a solid iron chloride, an activated carbon and the magnet sludges is heated and then distilled so that the chlorides of the corresponding rare earth elements and the iron chloride are separated and recovered. According to the invention, a neodymium oxide such as Nd2O3 can be efficiently recovered by converting the oxide into the corresponding chloride, but only an iron chloride (FeCl2) with high reducibility can be utilized as a reducing agent because the chemical reaction proceeds under a carbon-reducing atmosphere and high chlorine partial pressure atmosphere.
Reference 1: JP-A 2003-073754 (KOKAI)